Nitrogen-doped carbon black supported NiCo₂S₄ catalyst for hydrogenation of nitrophenols under mild conditions

Catalytic hydrogenation of nitrophenols to aminophenols was considered as the most efficient way to solve their contamination together with huge economic benefit. NiCo₂S₄ can be used not only as supercapacitor materials, but also competitive catalytic materials in hydrogenation reactions. In this work, a nitrogen-doped carbon black (NCB) supported NiCo₂S₄ catalyst is successfully prepared by a facile one-pot solvothermal approach. TEM results show that the ultrafine NiCo₂S₄ particles are uniformly dispersed on the surface of NCB at a low NiCo₂S₄ loading, while aggregation may occur in NiCo₂S₄/NCB catalysts with an excessive NiCo₂S₄ content. The NiCo₂S₄-30/NCB catalyst with a BET surface area of 47.20 m² g⁻¹ exhibits the most excellent catalytic activity and durability for heterogeneous catalytic hydrogenation of nitrophenols using NaBH₄ as the reducing agent at 30 °C in the aqueous solution. The kinetic constant of hydrogenation of p-nitrophenol catalyzed by NiCo₂S₄-30/NCB is almost five times higher than the reaction catalyzed by pristine NiCo₂S₄. The outstanding performance of NiCo₂S₄-30/NCB is ascribed to the unique nanostructure of the catalyst and the combined effect between the NiCo₂S₄ and NCB, including abundant surface functional groups of NCB for anchoring and dispersing NiCo₂S₄, strong adsorption ability for nitrophenol molecules facilitated by π–π stacking interaction, as well as fast electron transfer from NCB to NiCo₂S₄, resulting in higher local electron densities and thus facilitating the uptake of electrons by nitrophenols.